Not Applicable
Not Applicable
1. Field of the Invention
The field of the invention is clear coats for use on the exterior of substrates. More specifically, the invention relates to coatings applied to the exterior of golf balls.
2. Description of the Related Art
Clear coats are used on the exterior surfaces of a variety of substrates. Clear coats serve to enhance the aesthetic appearance of the substrate as well as act as a barrier to protect the substrate from weathering, mechanical agitation and the like. One such substrate in which clear coats are of particular importance is a golf ball.
A golf ball generally comprises a one-piece construction or it may include several layers including a core and an outer cover surrounding the core. Typically, one or more layers of paint and/or clearcoat are applied to the exterior surface of the golf ball. For example, in one typical design, the exterior surface of the golf ball is first painted with at least one clear or pigmented basecoat primer along with at least one application of a clear top coat. The basecoat and/or primer and clear top coat are applied to the golf ball to enhance the aesthetic appearance of the ball as well as mask or cover surface blemishes that may have resulted from the manufacturing process. The clear top coat is particularly important, in that the coat protects any markings, trademarks, logos, or the like that may be placed on the exterior surface of the ball.
Typically, the outer coating layers of a golf ball comprise a primer along with a clear urethane top coat. For example, U.S. Pat. No 5,459,220 discloses a two-pack urethane top coat for a golf ball that uses separate packages of a polyol and diisocyanate that employs biurets and isocyanurate trimers of hexamethylene diisocyanate (HDI) as the crosslinking agents. U.S. Pat. No 5,409,233 discloses a clear coating for use on a golf ball that incorporates a solvent system that includes methylamyl ketone.
Previous clear coat formulations had the disadvantage that they were preferably used with the addition of a basecoat or primer. The elimination of the basecoat or primer is desirous, since the basecoat increases the cost of manufacturing as well as increases the production time of the golf ball. In addition, the primer or basecoat can be the source of volatile organic compounds (VOC""s), that from an environmental standpoint, should be reduced or eliminated from the manufacturing process. Moreover, the presence of the primer coat can deleteriously affect the aerodynamic aspects of the golf ball during flight. The uneven distribution of primer over the cover as well as the pooling of primer within the dimples of the golf ball can alter the flight characteristics of the ball. In those instances where the clear coat could be applied directly to the exterior of the cover, the cover had to meet specific chemical requirements such as a high zinc content, or favorable adhesion characteristics.
Consequently, there remains a need for a clear coat that requires no basecoat or primer yet exhibits superior bonding to a variety of golf ball cover chemistries while still retaining superior abrasion resistance and durability.
In a first aspect of the present invention, a golf ball includes an exterior surface surrounded by a polyurethane coating. The polyurethane coating includes a polyester polyol resin containing a neopentyl glycol-based polyol resin, and a polyisocyanate component.
In a second aspect of the invention, a golf ball includes the polyurethane coating according to the first aspect of the invention, wherein the polyisocyanate component is an isocyanurate trimer of hexamethylene diisocyanate.
In a third, separate aspect of the invention, a polyurethane coating comprises a polyol component and a polyisocyanate component. The polyol component includes a mixture of neopentyl glycol resin, silane, aziridine, and a solvent blend including two or more of the solvents selected from the group consisting of ethyl acetate, butyl acetate, propyleneglycolmonomethylether acetate (PM acetate), toluene, or xylene. The polyisocyanate component contains a mixture of an isocyanurate trimer of hexamethylene diisocyanate, a biuret of hexamethylene diisocyanate, and the solvent blend.
Accordingly, it is an object of the present invention to provide a two-component polyurethane clear coat that is capable of being applied directly to a variety of substrates. The two-component polyurethane clear coat can be applied directly to the exterior surface of a golf ball with a wide range of chemistries without the use of a primer or basecoat. The clear coat can be applied and cured in a reasonably short period of time, thus reducing cycle times for the manufacture of balls. The elimination of the primer or basecoat permits greater aerodynamic predictability of the ball""s flight characteristics, as well as significantly reduces or eliminates emissions inherent in the primer/basecoat application process.
The benefits of the novel clear coat are superior resistance to yellowing and ultraviolet light degradation. The novel clear coat also has excellent adhesion to ionomers, elastomers, rubbers, and like materials that may be used as cover materials for golf balls. The novel clear coat also has superior abrasion resistance.